Mapping the magnetic susceptibility and electric conductivity of marine surficial sediments by benthic EM profiling

Müller, Hendrik; Dobeneck, Tilo von; Hilgenfeldt, Christian; SanFilipo, Bill; Rey, D.; Armesto, Belén Rubio

doi:10.1190/geo2010-0129.1

Cited by 44 publications

(19 citation statements)

References 46 publications

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“…For near‐seafloor surveys in shallow water, commercially available land EM systems can be adapted for marine use [e.g., Müller et al ., ; Goldman et al ., ], but in deep water (where, for example, gas hydrate is found), customized equipment must be developed. Deep‐water bottom‐towed electric and magnetic field systems have been developed and used effectively [ Cheesman et al ., ; Yuan and Edwards , ; Evans , ; Schwalenberg et al ., ; Schwalenberg and Engels , ].…”

Section: Introductionmentioning

confidence: 99%

Vulcan: A deep‐towed CSEM receiver

Constable

Kannberg

Weitemeyer³

2016

Geochem Geophys Geosyst

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We have developed a three‐axis electric field receiver designed to be towed behind a marine electromagnetic transmitter for the purpose of mapping the electrical resistivity in the upper 1000 m of seafloor geology. By careful adjustment of buoyancy and the use of real‐time monitoring of depth and altitude, we are able to deep‐tow multiple receivers on arrays up to 1200 m long within 50 m of the seafloor, thereby obtaining good coupling to geology. The rigid body of the receiver is designed to reduce noise associated with lateral motion of flexible antennas during towing, and allows the measurement of the vertical electric field component, which modeling shows to be particularly sensitive to near‐seafloor resistivity variations. The positions and orientations of the receivers are continuously measured, and realistic estimates of positioning errors can be used to build an error model for the data. During a test in the San Diego Trough, offshore California, inversions of the data were able to fit amplitude and phase of horizontal electric fields at three frequencies on three receivers to about 1% in amplitude and 1° in phase and vertical fields to about 5% in amplitude and 5° in phase. The geological target of the tests was a known cold seep and methane vent in 1000 m water depth, which inversions show to be associated with a 1 km wide resistor at a depth between 50 and 150 m below seafloor. Given the high resistivity (30 Ωm) and position within the gas hydrate stability field, we interpret this to be massive methane hydrate.

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Section: Introductionmentioning

confidence: 99%

Vulcan: A deep‐towed CSEM receiver

Constable

Kannberg

Weitemeyer³

2016

Geochem Geophys Geosyst

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“…The method has also been used to map the spatial distribution and composition of magnetic minerals in the coastal zone, to assess their degree of sorting, and to identify areas of sediment accumulation and erosion Hatfield et al, 2010;Zhang et al, 2010]. The technical ability to resolve magnetite distribution patterns in detail has been improved by the development of benthic electromagnetic profiling, which permits rapid mapping of magnetic susceptibility together with electrical conductivity [Müller et al, 2011[Müller et al, , 2012. This sample-based study is aimed at deepening fundamental understanding of geological and hydrodynamic processes as a prerequisite for future high-resolution mapping and modeling.…”

Section: Introductionmentioning

confidence: 99%

Formation of magnetite‐enriched zones in and offshore of a mesotidal estuarine lagoon: An environmental magnetic study of Tauranga Harbour and Bay of Plenty, New Zealand

Badesab

Dobeneck

Bryan

et al. 2012

Geochem Geophys Geosyst

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[1] Magnetic iron minerals are widespread and indicative sediment constituents in estuarine, coastal and shelf systems. We combine environmental magnetic, sedimentological and numerical methods to identify magnetite-enriched placer-like zones in a complex coastal system and delineate their formation mechanisms. Magnetic susceptibility and remanence measurements on 245 surficial sediment samples collected in and around Tauranga Harbour, the largest barrier-enclosed tidal estuary of New Zealand, reveal several discrete enrichment zones controlled by local hydrodynamic conditions. Active magnetite enrichment takes place in tidal channels, which feed into two coast-parallel nearshore magnetite-enriched belts centered at water depths of 6-10 m and 10-20 m. A close correlation between magnetite content and magnetic grain size was found, where higher susceptibility values are associated within coarser magnetic crystal sizes. Two key mechanisms for magnetite enrichment are identified. First, tide-induced residual currents primarily enable magnetite enrichment within the estuarine channel network. A coast-parallel, fine sand magnetite enrichment belt in water depths of less than 10 m along the barrier island has a strong decrease in magnetite ©2012. American Geophysical Union. All Rights Reserved.1 of 20 content away from the southern tidal inlet and is apparently related to active coast-parallel transport combined with mobilizing surf zone processes. A second, less pronounced, but more uniform magnetite enrichment belt at 10-20 m water depth is composed of non-mobile, medium-coarse-grained relict sands, which have been reworked during post-glacial sea level transgression. We demonstrate the potential of magnetic methods to reveal and differentiate coastal magnetite enrichment patterns and investigate their formative mechanisms.

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“…특히 소형 루프형 전자탐사를 해양 환경에서 적용하는 연구들 은 국내에서 뿐만 아니라 국제적으로도 시간영역(time domain) (Nakayama and Saito, 2011;Swidinsky et al, 2012) 및 주파수 영역에서 (Ko et al, 2012;Müller et al, 2012;Müller et al, 2011 (Nabighian, 1988;Zhdanov et al, 2006) Ko et al (2012)). Note that the anomaly appears as a face-to-face ellipses shape and is marked in a circle.…”

Section: 고휘철·박인화·이성곤unclassified

Response Analysis of Data Acquired by Marine Loop Electromagnetic System Using Three-Dimensional Modeling Based on Integral Equation

Ko¹,

Park²,

Lee³

2014

Geophysics and Geophysical Exploration

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Abstract:We analyzed response patterns of test field data acquired with new small loop electromagnetic (EM) system using three-dimensional (3D) electromagnetic modeling code. The size and shape of a conductor was adopted as experimental parameters for EM modeling to understand influencing factors of the response patterns due to a metallic object on the seafloor. Obtaining the responses for four models of difference sizes and shapes through 3D EM modeling, we confirmed that the shape of the object have a more critical factor on the response pattern than size. We also calculated "ppm" values with respect to different altitudes of the sensor and source frequencies. The modeling results show that the consistency of sensor altitude is important and imaginary part of ppm response is more sensitive than real part. We also visualized the contour map of the real and imaginary part of ppm value as a function of frequency and altitude so that we can estimate proper altitude for source frequency band of our survey system. The results of this paper are anticipated to give proper parameters in survey construction for seafloor massive sulfide deposit.

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Mapping the magnetic susceptibility and electric conductivity of marine surficial sediments by benthic EM profiling

Cited by 44 publications

References 46 publications

Vulcan: A deep‐towed CSEM receiver

Vulcan: A deep‐towed CSEM receiver

Formation of magnetite‐enriched zones in and offshore of a mesotidal estuarine lagoon: An environmental magnetic study of Tauranga Harbour and Bay of Plenty, New Zealand

Response Analysis of Data Acquired by Marine Loop Electromagnetic System Using Three-Dimensional Modeling Based on Integral Equation

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